erofs-linux/tools/lib/perf/Documentation/examples/sampling.c

#include <linux/perf_event.h>
#include <perf/evlist.h>
#include <perf/evsel.h>
#include <perf/cpumap.h>
#include <perf/threadmap.h>
#include <perf/mmap.h>
#include <perf/core.h>
#include <perf/event.h>
#include <stdio.h>
#include <unistd.h>

static int libperf_print(enum libperf_print_level level,
                         const char *fmt, va_list ap)
{
	return vfprintf(stderr, fmt, ap);
}

union u64_swap {
	__u64 val64;
	__u32 val32[2];
};

int main(int argc, char **argv)
{
	struct perf_evlist *evlist;
	struct perf_evsel *evsel;
	struct perf_mmap *map;
	struct perf_cpu_map *cpus;
	struct perf_event_attr attr = {
		.type        = PERF_TYPE_HARDWARE,
		.config      = PERF_COUNT_HW_CPU_CYCLES,
		.disabled    = 1,
		.freq        = 1,
		.sample_freq = 10,
		.sample_type = PERF_SAMPLE_IP|PERF_SAMPLE_TID|PERF_SAMPLE_CPU|PERF_SAMPLE_PERIOD,
	};
	int err = -1;
	union perf_event *event;

	libperf_init(libperf_print);

	cpus = perf_cpu_map__new_online_cpus();
	if (!cpus) {
		fprintf(stderr, "failed to create cpus\n");
		return -1;
	}

	evlist = perf_evlist__new();
	if (!evlist) {
		fprintf(stderr, "failed to create evlist\n");
		goto out_cpus;
	}

	evsel = perf_evsel__new(&attr);
	if (!evsel) {
		fprintf(stderr, "failed to create cycles\n");
		goto out_cpus;
	}

	perf_evlist__add(evlist, evsel);

	perf_evlist__set_maps(evlist, cpus, NULL);

	err = perf_evlist__open(evlist);
	if (err) {
		fprintf(stderr, "failed to open evlist\n");
		goto out_evlist;
	}

	err = perf_evlist__mmap(evlist, 4);
	if (err) {
		fprintf(stderr, "failed to mmap evlist\n");
		goto out_evlist;
	}

	perf_evlist__enable(evlist);
	sleep(3);
	perf_evlist__disable(evlist);

	perf_evlist__for_each_mmap(evlist, map, false) {
		if (perf_mmap__read_init(map) < 0)
			continue;

		while ((event = perf_mmap__read_event(map)) != NULL) {
			int cpu, pid, tid;
			__u64 ip, period, *array;
			union u64_swap u;

			array = event->sample.array;

			ip = *array;
			array++;

			u.val64 = *array;
			pid = u.val32[0];
			tid = u.val32[1];
			array++;

			u.val64 = *array;
			cpu = u.val32[0];
			array++;

			period = *array;

			fprintf(stdout, "cpu %3d, pid %6d, tid %6d, ip %20llx, period %20llu\n",
				cpu, pid, tid, ip, period);

			perf_mmap__consume(map);
		}

		perf_mmap__read_done(map);
	}

out_evlist:
	perf_evlist__delete(evlist);
out_cpus:
	perf_cpu_map__put(cpus);
	return err;
}